While the ABS light is on you can have the ABS codes read. That would tell you for sure it is the rears and possibly something useful.
The SS rear hubs are a different part number from LT/LS hubs. Maybe that's why.

 

im working on swapping the hubs today, but ive already got one bolt stripped, another with a rusted stuck nut, and a bleeder screw stripped. i swear, this hhr hates me. the 07 didnt give me any trouble at all but the 11 was one of the last to roll off the line and spent its first 46k and 8+ years in salty ass PA and has been nothing but a PITA. ahh well...theyre a great looking car at least

btw...according to GMPartsDirect my 11LT hub part # 15889806 fits/is compatible for the 08SS but the SS part # 15798483 is listed as not compatible with the 11LT. very odd. i checked before i pulled my hubs. hopefully this is the culprit and hopefully i can get all of these issues worked out today.

 

"fits" and "same" don't means the same thing. I don't trust anything related to SS that says "fits all".

I just looked the part numbers up in Mitchell OnDemand for another thread, they are different parts and the SS cost $79 more.
Your 15798483 does crossover to 20907864

2009 SS w ABS $279 ea.
GM 20907864
AC/Delco RW20-138

2009-2011 LT/LS w ABS $200 ea.
GM 15889806
AC/Delco RW20-107

 

fwiw i swapped the hubs and all lights went off

 

To confirm, you put the 2011 hubs from the drum brake axle in the SS axle and that cleared your ABS light. Awesome!